1. Field of the Invention
The present invention relates to disengageable linear stepper electric motors of the type comprising a multipole stator in the bore of which a rotor of smaller diameter revolves cycloidally.
To transform this rotational movement into a linear axial movement, the bore of the stator is tapped whereas the rotor comprises on its peripheral portion parallel scores or else a thread compatible with the tapping of the stator. A drive rod, axially fast with the rotor, is thus driven in linear translation.
2. Description of the Prior Art
Motors of this type are already known, an example is described in the European patent application No. 0 078 740.
Such devices are used particularly for controlling regulation systems. In these systems, the drive rod, which moves linearly and step by step controls regulation members. It is often called control rod.
A characteristic of these devices is that, if special precautions are not taken, the motor bathes in the gas or liquid medium to be regulated.
This is of little importance when this medium is air, for example, but the same cannot be said when this medium comprises dangerous, particularly explosive, liquids or gases.
In this case, since the stator environment is an electrically active environment, there is a danger of explosion. In addition, it is generally necessary that the motor does not offer to the dangerous liquid or gas a passage to the outside environment which must remain protected.